The present invention relates in general to air filters which are intended for trucks and related vehicles and which are of the type using a cylindrical, pleated paper filtering element. More particularly, the present invention relates to the design of a seal member placed between one end of the filtering element and a filter housing so that air entering the housing passes through the filtering element before exiting from the filter housing.
The task of sealing a pleated paper filtering element within a filter housing has been attempted in a number of different ways. One approach used in certain designs is to compress the outlet end of the filter element against the end wall of the housing, with a gasket disposed between the end of the filter element and the housing end wall. An illustration of this design approach is shown in U.S. Pat. No. 3,078,650 which issued Feb. 26, 1963 to Anderson et al.
A variety of latches and clamping devices have been used to effect a positive clean air seal in air filter assemblies. However, the use of axial compression sealing techniques requires that the filter elements be constructed so as not to collapse under compression, and requires the use of relatively heavy-gauge steel in the housing. Because both the filter housing and the filter element must be strong and rigid when using such techniques, improvements in the area of low-cost, lightweight elements in housings have been slowed. Nevertheless as to the filter housing, non-engineering grades of plastic as well as some molding processes have been envisioned as a possibility for lower cost and lighter weight. U.S. Pat. No. 4,720,292 which issued Jan. 19, 1988 to Engel et al. is representative of attempts to use certain grades of plastics and other materials in order to create a lightweight housing. In Engel et al., a positive clean air seal is established between the radially inwardly facing surface of the filter element end cap and a tubular air outlet member so that there is no need to axially compress the filter element as in earlier designs in order to achieve a seal between the end of the filter element and the housing. In what is described as the preferred embodiment of Engel, this particular design intention is accomplished by molding a ring-like end cap at the open end of the filter element from a urethane foam material having a relatively soft, rubber-like consistency. The cylindrical inner surface of this gasket is constructed and arranged to fit around and sealingly engage (radial compression) an inner end portion of a tubular air outlet member. In this manner, a relatively lightweight housing can then be provided to channel the flow of air through the filter element. No mechanical aids or clamps are necessary to exert outside sealing force because the seal is self-generated when the end cap is inserted over and around the tubular outlet member. Although Engel may represent a current approach in the use of lightweight materials for the outer housing, there are other design approaches relating to air filters, air cleaners and seal designs which have been conceived over the years. The following patent references are representative of some of these other design approaches:
______________________________________ Patent/Publication Issue/Publication No. Patentee/Inventor Date ______________________________________ 4,488,889 McCarroll December 18, 1984 4,759,783 Machado July 26, 1988 4,950,317 Dottermans August 21, 1990 5,030,264 Klotz et al. July 9, 1991 WO 91/13675 Machado September 19, 1991 O 470 330 Al(EP) Behrendt April 6, 1991 O 470 328 Al(EP) Benzler March 30, 1991 5,043,114 Saito et al. Aug. 27, 1991 4,113,627 Leason Sep. 12, 1978 4,350,509 Alseth et al. Sep. 21, 1982 4,838,901 Schmidt et al. Jun. 13, 1989 5,082,476 Kahlbaugh et al. Jan. 21, 1992 3,906,724 Yoshizaki Sep. 23, 1975 4,443,237 Ulvestad Apr. 17, 1984 5,120,337 Benzler et al. Jun. 9, 1992 5,167,683 Behrendt et al. Dec. 1, 1992 ______________________________________
In contrast to the approach followed by these earlier designs as represented by the identified patents, Raines et al. pursued a different approach as is disclosed in U.S. filed Nov. 4, 1993, now abandoned. The '647 application discloses a sealing element (gasket) which is configured so as to provide three sealing portions which work independently of each other but which combine to provide a design with improved reliability and effectiveness. One sealing portion is a radial seal which is arranged so as to be placed in tension for sealing instead of being placed in compression. Another sealing portion, also in tension, is created by axial interference and the third sealing portion uses axial compression. The Raines et al. invention is such that the sealing gasket can be applied to a conventional metal end plate as positioned over one end of the filtering element. The Raines et al. invention may also be used within a housing of the design provided in the 4,720,292 Engel patent but without the use of the molded urethane end cap 25.
The present invention improves upon the Raines et al. approach as disclosed in the '647 application and upon the Engel ('292) approach by maintaining three different sealing mechanisms, but doing so by means of a molded, unitary, polyurethane end cap which fits over the end of the filter media, precluding the separate use of an endplate (item 46 in Raines et al.). The present invention also improves upon the Engel ('292) approach which does disclose a molded end cap (25), by the specific style and shape of the engaging sealing portion of the molded end cap. The molded end cap/seal combination of the present invention performs the combined functions of the end cap, an adhesive compound such as "Plastisol", the sealing gasket and any additional glue or the adhesive of earlier designs.
The molded end cap and gasket combination of the present invention provides all of its sealing interfaces at locations which are below the plane of the lower surface of the filter element and sealing is accomplished through three different mechanisms. When the filter is installed, the sealing portion of the present invention gasket is deflected and placed in tension around the center post of the air filter housing. The lower surface of the present invention gasket is placed in compression against the bottom of the air filter housing by installing the air filter housing cover. Finally, differential pressure forces cause the gasket to seal more tightly against the center post of the housing during engine operation.
The easiest way to view the present invention relative to the prior work of Raines et al. ('647) and Engel et al. ('292) is to first recognize that the molded end cap design of the present invention can be used in either of these two housing styles. Raines et al. provides a heavier package with axial clamping while Engel et al. focuses more on a lightweight, plastic construction without the higher levels of axial clamping force. Further, the present invention employs a molded end cap, as does Engel et al., and three modes of sealing, as is provided by Raines et al. However, the present invention pursues a completely different approach than is what is represented by the molded end cap of Engel et al. and the style of seal in the present invention is significantly different from what has been provided by the Raines et al. disclosure.
According to the present invention the end cap portion of the combination provides radial sealing against the center post of the filter housing but provides such radial sealing by means of tension rather than being placed in compression as is done in the Engel et al. design. This makes the present invention somewhat more forgiving as to the various dimensions and tolerances and provides greater ease as to its construction and assembly. The present invention does not require a back-up support surface for radial compression as is required by the Engel et al. design. The three types of modes of sealing provide greater reliability and seal integrity. The geometry, size, shape and location of the sealing portion of the end cap of the present invention is unique over any of the earlier patent references or other disclosures.
There are in fact other patent references which were made of record in the first and second reexaminations of Engel et al. (B1 4,720,292 and B2 4,720,292) and which have not been listed or mentioned above. Since the focus of Engel et al. is on the specific style and geometry of a molded end cap, and since the present invention embodies a molded end cap, some of these other patent references may be regarded as pertinent and the selected references include the following:
______________________________________ Patent/Publication Issue/Publication No. Patentee/Inventor Date ______________________________________ 2,962,121 Wilber Nov. 29, 1960 3,147,100 Wilber Sep. 1, 1964 3,169,844 Young Feb. 16, 1965 3,672,130 Sullivan et al. Jun. 27, 1972 4,128,251 Gaither et al. Dec. 5, 1978 4,135,899 Gauer Jan. 23, 1979 4,159,197 Shuler et al. Jun. 26, 1979 4,211,543 Tokar et al. Jul. 8, 1980 4,227,898 Kamekawa et al. Oct. 14, 1980 4,235,611 Brownell Nov. 25, 1980 4,491,460 Tokar Jan. 1. 1985 4,609,465 Miller Sep. 2, 1986 2 268 551 French-Girard Nov. 21, 1975 2 261 041 French-Mavel Sep. 12, 1975 59-141150 Japan-Fukumoto et al. Sep. 20, 1984 4,349,363 Patel, et al. Sep. 14, 1982 4,369,113 Stifelman Jan. 18, 1983 4,507,203 Johnston Mar. 26, 1985 5,112,372 Boeckermann et al. May 12, 1992 5,250,179 Spearman Oct. 5, 1993 ______________________________________
While there are a wide variety of filter housings, gaskets and sealing concepts represented by these listed references, none anticipate nor render obvious the present invention.